The combat is still easy even on hardest difficulty setting. Even with puppet mode on NPCs I didn't find the combat very tactical compared to say Icewind Dale series, not that the combat was heavy on strategy in those games, but there were lot of well designed battles. I think the design focus in NWN2 was rather on plot than in combat, not that there is anything wrong in that.

If I recall right in NWN2 enemies do pretty much the same thing. Melee enemies always just run to you. Ranged enemies always use a bow and spellcasters just fling magic missile or chain lightning on higher levels. The AI can be improved but it still wouldn't make combat that much harder since most of the time the enemies have been placed on a clean map right in front of players with no traps between them or any other objects or hazards on the map that would complicate the battle. The traps also don't pose enough threat, I don't remember I saw any flesh to stone or finger of death traps in NWN2.

For example of a nicely designed battle that used map design to complicate things, in IWD2 there was that goblin fortress where you had to sneak in and take down drums that would summon tough monsters when goblin shamans banged them. Only that the drums were on the other side of canyon. There were few bridges that you could cross, but they were guarded by monsters and ofcourse trapped. But anyway that was the front yard of the fortress, you had to continue through a tunnel to get inside the fortress and eventually take down everything there.

Edit: For NWN2's sake, it did involve some memorable battles like the two black dragons, the red dragon (especially if you got the dragon to assault the giants and double crossed it), the siege defense, the battle with several Reavers and the final battle with KoS. Though they standed out more of novel feature than tactical combat once you figured out all the buff spells you had available like energy immunity and stone skin.